IIT-JEE 2010 · Paper 2 · Chemistry Q10

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ChemistryInteger+3Question 10 of 57

Silver (atomic weight = 108 g mol⁻¹) has a density of 10.5 g cm⁻³. The number of silver atoms on a surface of area $10^{-12}$ m² can be expressed in scientific notation as $y\times10^{x}$ . The value of $x$ is

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Answer and worked solution

Official answer: 7

Atoms per volume.
$n=\frac{10.5}{108}\times6.022\times10^{23}=5.86\times10^{22}\ \mathrm{cm^{-3}}.$

Atoms per area. Treat the atoms as on a simple grid: per length $n^{1/3}=3.88\times10^7\ \mathrm{cm^{-1}}$ , so per area $n^{2/3}=1.51\times10^{15}\ \mathrm{cm^{-2}}=1.51\times10^{19}\ \mathrm{m^{-2}}$ .

On $10^{-12}$ m². $1.5\times10^7$ atoms, so $x=7$ .

Answer: 7

Topics:Mole concept

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IIT-JEE 2010 · Paper 2, Chemistry question 10